Not applicable.
(1) Field of the Invention
The present invention relates generally to systems and methods for measuring relatively short distances preferably by utilizing a combination of electromagnetic and acoustic signaling. More particularly, the present invention is especially suitable for electronically measuring the distance between a plurality of objects that may be in relative motion or formation with respect to each other and which may be moving at relatively high speeds with respect to other objects in underwater or airborne environments.
(2) Description of the Prior Art
Typical methods of electronically measuring distances between objects may include use of RADAR, LIDAR, or other systems. However, in many cases such moving objects or vehicles may contain various electronic communications equipment with the result being that the electronic systems may frequently interfere and confuse each other when multiple short-range objects are targets are in range.
Future Navy systems may deploy one or more groups of autonomous stealthy objects that may function together to perform one or more needed functions, e.g., a large-aperture electromagnetic collection system or high-bandwidth communications link. The objects and/or groups of objects may be required to move together as a unit within tens of meters while maintaining a predetermined one-to-another positional relationship or formation. When the relative separations among the individual objects are larger, an independent position locating system, e.g., GPS, RADAR, and the like, may be used by the plurality of autonomous vehicles to maintain their relative positions within a specified envelope. However, systems such as GPS and others may often have rather limited accuracy with respect to close distances of ten or twenty meters or less, processing time constraints, reception interference problems, and so forth. It would be desirable to provide a method that can be utilized to determine and/or maintain the relative position of a plurality of objects moving together in a selectable formation whereby the objects may be within a few meters of each other and whereby accuracy of the relative positions of each object may be rapidly and repeatedly calculated with accuracy in the millimeter to centimeter range being easily achievable.
Various inventors have attempted to solve related problems as evidenced by the following patents.
U.S. Pat. No. 6,160,493, issued Dec. 12, 2000, to E. T. Smith, discloses a low-cost and reliable radio warning system 12 that alerts system users to potentially hazardous conditions. The system makes use of a transmitter and at least one receiver. The transmitter generates and transmits a radio warning signal that carries a digital data sequence that includes information concerning a particular potential hazardous condition from which the transmission was initiated, such as an approaching ambulance, fire truck, bus, train, or the like. Other information, such as GPS coordinates, may also be included. Through the use of digital encoding techniques, the system""s susceptibility to false alarms or xe2x80x9cfalse triggersxe2x80x9d is minimized. The radio warning signal is transmitted in burst transmissions and may use a number of signaling techniques, including spread spectrum transmission, which increases system reliability and performance even in the presence of interference or multipath distortion. System users are equipped with a receiver that receives the radio warning signal and interprets the digital data and information carried by the warning signal. The receiver alerts the system user who has received the radio warning signal of the potential hazardous condition through the use of an audible, visual or tactile alarm. Based on the simplicity of its design, the receiver is intended to be small enough to be a portable, hand held-device, or installed or mounted in a user""s motor vehicle so that persons carrying the receiver and motor vehicle operators alike can be alerted of potentially hazardous conditions by receiving a radio warning signal of the present invention.
U.S. Pat. No. 6,104,671, issued Aug. 15, 2000, to Hoyt et al, discloses an apparatus and method for measuring the true distance and relative velocity between first and second objects. The apparatus comprises a transceiver located at the first object which measures a first transit time for the transmission of a first signal from a first object to a second object and for the reflection of the first signal from the second object back to the first object. The transceiver further measures a second transit time for the transmission and reflection of a second signal, the second signal being transmitted immediately upon the reflection of the first signal back to the first object. First and second transit times can be used to calculate first and second apparent distances between the first and second objects, respectively. The apparatus also includes calculating means for determining the relative velocity between the first and second objects using the first transit time and the second transit time. The calculating means calculates the true distance between the first and second objects at the time of reflection of the second signal by modifying the second apparent distance in accordance with the relative velocity between the first and second objects during the time of transmission and reflection of the second signal.
U.S. Pat. No. 5,983,161, issued Nov. 9, 1999, to Lemelson et al., discloses GPS satellite ranging signals received on comm1, and DGPS auxiliary range correction signals and pseudolite carrier phase ambiguity resolution signals from a fixed known earth base station received on comm2, wherein information related to one of a plurality of vehicles/aircraft/automobiles is computer processed to continuously determine the one""s kinematic tracking position on a pathway with centimeter accuracy. That GPS-based position is communicated with selected other status information to each other one of the plurality of vehicles, to the one station, and/or to one of a plurality of control centers, and the one vehicle receives therefrom each of the others"" status information and kinematic tracking position. Objects are detected from all directions by multiple supplemental mechanisms, e.g., video, radar/lidar, laser and optical scanners. Data and information are computer processed and analyzed in neural networks in the one vehicle to identify, rank, and evaluate collision hazards/objects, an expert operating response to which is determined in a fuzzy logic associative memory which generates control signals which actuate a plurality of control systems of the one vehicle in a coordinated manner to maneuver it laterally and longitudinally to avoid each collision hazard, or, for motor vehicles, when a collision is unavoidable, to minimize injury or damage therefrom. The operator is warned by a heads up display and other modes and may override. An automotive autopilot mode is provided.
U.S. Pat. No. 5,798,983, issued Aug. 25, 1998, to Kuhn et al., discloses a multi-lane traffic monitoring system based on detecting the acoustic signals motor vehicles create and radiate during operation. The system comprises an array of electro-acoustic sensors for converting impinging acoustic wavefronts to analog electrical signals; a circuit to acquire, perform signal frequency component discrimination, and digitize the electrical signals at the electro-acoustic sensor array output; a circuit to perform effective spatial discrimination in the up/down road direction and in the cross-road direction in real time; a circuit to perform vehicle detection for individual lanes and to estimate or measure pertinent parameters associated with each vehicle detection from each traveled lane; and a circuit to compute for each lane, pertinent traffic flow parameters from vehicle parameters for the purpose of providing a transportation system interface. In accordance with another embodiment, a circuit is provided to automatically scan for acoustic sources in the cross-road direction and to automatically identify each highway lane direction relative to it the physical electro-acoustic sensor array orientation. In accordance with still another embodiment, a circuit is provided via signal frequency component discrimination and signal processing to create, from a single physical sensor, two vehicle detection zones within each highway lane, wherein a smaller detection zone is located inside a larger detection zone. A circuit is also provided to measure the time between initial vehicle detection in the larger (outer) detection zone and initial vehicle detection in the smaller (inner) detection zone, wherein vehicle speed is determined from the initial detection time difference. In accordance with yet another embodiment, a circuit is provided to measure the relative position of the sound radiated from each of a vehicle""s tires and determine vehicle type classification associated with each vehicle detection and with each measured vehicle speed.
U.S. Pat. No. 6,021,364, issued Feb. 1, 2000, to Berliner et al., discloses a method and apparatus for acoustically monitoring a highway which is inexpensive to maintain and install and which does not require that the roadway be closed, torn-up or repaved. These results are obtained in an illustrative embodiment of the present invention which comprises a Mill""s Cross acoustic array mounted proximate to a highway, spatial discrimination circuitry, frequency discrimination circuitry and interface circuitry that generates a binary signal which indicates when a motor vehicle is, or is not, within a detection zone on the roadway.
U.S. Pat. No. 5,933,099, issued Aug. 3, 1999, to J. Mahon, discloses a collision avoidance system for a warning aircraft which includes a transmitter and receiver for interrogating the transponder of a warned aircraft. A computer to be installed in the warning aircraft is programmed with the distances or rates of closure at which the warning aircraft and the warned aircraft constitute traffic for one another. When the computer has determined that the warning aircraft and a warned aircraft constitute traffic for one another, a warning system broadcast an appropriate vocal warning.
U.S. Pat. No. 5,872,526, issued Feb. 16, 1999, to B. Tognazzini, discloses a collision avoidance system for a plurality of vehicles equipped with GPS receivers, each broadcasting current location information to other vehicles and receiving and displaying location information from other vehicles, which enables a vehicle operator to be aware of the location of the other vehicles. For vehicles not equipped with GPS, and transceivers, information about location is taken from common ground control equipment such as a FAA control station and broadcast to all vehicles. In an aircraft environment, flight plans can be filed and closed out automatically.
U.S. Pat. No. 5,493,309, issued Feb. 20, 1996, to J. E. Bjornholt, discloses a collision avoidance communication system and method with equipped aircraft and ground control stations that represent nodes of a RF communication network. A radar system determines locations of equipped aircraft and unequipped aircraft within an airspace. The ground control station couples to the radar system and the network to receive location data for the aircraft. These location data are merged in an object list. The ground control station displays objects from the object list, broadcasts surrogate location data for unequipped aircraft over the network, and broadcasts control data describing weather conditions, geographic features, and the like, over the network. Equipped aircraft receive aircraft location data and control data from the network. Each equipped aircraft determines its own location. The equipped aircraft include a display which shows the locations and orientations of nearby aircraft and of geographic features, and the equipped aircraft broadcast their own locations over the network.
U.S. Pat. No. 5,596,332, issued Jan. 21, 1997, to Coles et al., discloses an aircraft location and identification system including a first position determining portion located aboard a transmitting aircraft for determining a first set of present positional and tracking information is described relative to said transmitting aircraft. A transmitting portion is included for transmitting the first set of present positional and tracking information to a receiving aircraft. A second position determining portion, which is located aboard the receiving aircraft, determines a second set of present positional and tracking information relating to the receiving aircraft. A computing portion is located aboard the receiving aircraft and/or a ground based facility. The computing portion utilizes present and past values of the first set of present positional and tracking information to derive a corresponding first probabilistic future tracking configuration of the transmitting aircraft. The computing portion also utilizes present and past values of the second set of the present positional and tracking information to derive a corresponding second probabilistic future tracking configuration of the receiving aircraft.
U.S. Pat. No. 5,381,338, issued Jan. 10, 1995, to Wysocki, et al., discloses a positioning, navigation and collision avoidance system for ships, aircraft, land vehicles and the like, which utilizes a geo-referenced digital orthophotograph data-base and a positioning signal to display upon a computer stereo graphics device a high visibility dynamic photographic image of the user""s immediate environment, including both moving and stationary obstacles. The position and temporal data along with the geo-referenced elevation data utilized to derive the digital orthophotograph(s) can serve to warn the user of nearby obstacles; and optionally, to implement semi-automatic avoidance. Substituting user generated x-y-z positions and times, the system may be used in a static mode as a flight simulator or a simulator for other modes of transportation. The system may also be used as a mobile Geographic Information Systems decision making tool with the addition of user supplied geo-referenced digital data layers.
U.S. Pat. No. 5,347,546, issued Sep. 13, 1994, to Abadi et al., discloses a method and apparatus for pre-filtering a global positioning system receiver, which includes the steps of: receiving a plurality of L-band radio frequency signals having unique modulation and originating in a plurality of global positioning system satellites; splitting the plurality of radio frequency signals into at least a first L1 radio frequency signal and a second L2 radio frequency signal; passing the first L1 radio frequency signal to a first radio frequency receiving section through a L1 signal passage defining a path from a common junction point to the L1 radio frequency receiving section, while simultaneously passing the L2 radio frequency signal to a second radio frequency receiving section through a L2 signal passage defining a path from the common junction point to the L2 radio frequency receiving section; filtering the L1 radio frequency signal from the L2 signal passage and filtering the L2 radio frequency signal from the L1 signal passage, while substantially preserving the L1 radio frequency and the L2 radio frequency signals; and feeding the L1 and the L2 radio frequency signals to the first L1 radio frequency receiving section and the second L2 radio frequency receiving section, for determining position information.
U.S. Pat. No. 5,181,027, issued Jan. 19, 1993, to T. R. Shafer, discloses an improved air traffic control (ATC) system which utilizes traffic alert and collision avoidance systems (TCAS) as a component together with a flight control computer of an aircraft autopilot, a data radio and an interactive touch screen display device to produce a system for allowing easy trailing of another aircraft on trans-oceanic flights and to reduce landing delays at busy airports under IFR conditions.
Consequently, there remains a long felt but unsolved need for improved short distance locating system that may be used for orientation of individual objects and/or one or more groups of objects which may be in tight formation relative to individual objects, targets, and/or other groups, and which move within an environment possibly at high speeds. Those skilled in the art will appreciate the present invention that addresses the above and other problems.
Accordingly, it is an objective of the present invention to provide an improved system and method for measuring short distances.
Another objective is to provide a system and method as aforesaid which provides a system and method for determining relative distances between one or more objects, and/or one or more groups of objects.
A further objective is to provide a system and method as aforesaid whereby transponders responsive to query signals are provided and whereby acoustic signals may preferably be responsively transmitted by the transponders.
A still further objective is to provide a system and method as aforesaid whereby the query may be provided electromagnetically, acoustically, or by other transmission means.
Yet another objective is to provide a system and method as aforesaid which is of special utility whereby the environment in which the objects move may comprise an underwater environment, airborne environment, underground environment, or other environments.
These and other objectives, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims. However, it will be understood that above listed objectives and advantages of the invention are intended only as an aid in understanding aspects of the invention, are not intended to limit the invention in any way, and do not form a comprehensive list of objectives, features, and advantages.
In accordance with the present invention, a short distance measuring system for measuring distances less than 20 meters is provided that is operable within an environment and may comprise elements such as, for instance, a plurality of moveable objects moveable independently of each other within the environment. Each of the plurality of moveable objects may have a transponder mounted thereto operable for receiving a query signal and producing a response signal. The invention may provide a plurality of synchronized clocks. A synchronized clock system is provided to produce synchronized timing signals. In one embodiment, the synchronized clock system provides that each of the plurality of moveable objects have mounted thereto a respective one of a corresponding plurality of synchronized clocks. Each of the synchronized clocks may be operable for producing the synchronized timing signals. The synchronized timing signals may or may not be broadcast to maintain synchronization. Alternatively, broadcast timing signals may be used without the need for multiple clocks. Each of the transponders may be operable for producing a response signal in response to the query signal at a start time based on the synchronized timing signal. A response signal detector may be provided for each of the plurality of moveable objects. The response signal detector is preferably operable to measure a transit time for the response signal beginning at the start time based on the synchronized timing signals and ending upon detection of the response signal at a respective moveable object. The response signal detector may be operable for measuring a magnitude of one or more separation vectors between the plurality of moveable objects utilizing a respective transit time.
In one embodiment, the query signal is an electromagnetic signal and the response signal is an acoustic signal. In another embodiment, the electromagnetic signal comprises a pseudo noise code. The electromagnetic signal may further comprise location information data related to the plurality of moveable objects. Still further basic embodiments are possible, including one in which as in preceding the signal responsively transmitted by the transponders is in the form of an acoustic signal, and the query signal is also an acoustic signal. In yet further alternate embodiments, the query signal could be in the forms of infrared signals, other forms of optical signals, or magnetic pulse signals.
The system may further comprise one or more fixed position transponders which may have a fixed location with respect to the environment such that each of the fixed position transponders may be operable for producing an acoustic signal in response to the query signal.
In operation, a method is provided comprising one or more steps, such as, for instance, providing a plurality of synchronized clocks at a plurality of locations, transmitting at least one electromagnetic query signal from the one or more moveable objects, receiving said transmitted at least one electromagnetic query signal, responding to said transmitted at least one electromagnetic query signal by generating at least one acoustic signal such that said at least one responsively transmitted acoustic signal is transmitted at a start time based on timing of the synchronized clocks, measuring a transit time of said responsively generated at least one acoustic signal to the one or more objects by measuring a time beginning at the start time and ending upon receipt of said responsively transmitted at least one acoustic signal, and determining a distance based on the transit time.
Other steps might include providing one or more transponders moveable within the environment operable for effecting the steps of receiving and transmitting and/or mounting respective of the one or more transponders to respective of the one or more moveable objects and/or mounting one more transponders to be affixed in position with respect to the environment.
The method may further comprise sending transponder identity information from the one or more transponders to identify a respective transponder that produces said responsively transmitted at least one acoustic signal and/or updating location information regarding a location of the one or more moveable objects within the environment and/or transmitting the location information utilizing an electromagnetic signal.
Thus, the present invention provides a short distance measuring system for an environment which may comprise one or more elements such as, for instance, one or more moveable objects moveable within the environment, a transmitter for the one or more moveable objects operable for transmitting location information regarding a position of the one or more moveable objects within the environment and/or operable for transmitting a query signal, one or more transponders operable for producing a response signal in response to the query signal such that the response signal may be detectable by the one or more moveable objects, a plurality of synchronized clocks for the one or more transponders and for the one or more moveable objects so that the response signal is produced at a start time based upon a timing of the plurality of synchronized clocks, a transit-time measurement detector operable to measure a transit time of the response signal beginning at the start time and ending upon detection of the response signal by the one or more objects whereby the transit-time measurement detector may be operable for measuring a magnitude of a separation vector between the one or more moveable objects and the one or more transponders.
The system may further comprise a control system for maintaining a desired magnitude of the separation vector. In one embodiment, the control system is operable for automatically maintaining a desired formation of a plurality moveable objects by monitoring a plurality of corresponding of separation vectors. In a further embodiment, the system may comprise an information system for an operator or visitor desirous of determining his/her way in navigating through a complex environment, such as a large building complex. In this system, the moveable object transmitting a query signal may be a handheld, portable, battery-operated device which co-acts with acoustic transponders fixedly mounted within the environment.